I examine the ways in which words such as "evidence" are used inappropriately to support policy that may be formulated for convenience, cost or political dogma. I interrogate the processes by which this happens, as words and terms are bestowed with symbolic power to support and promote favoured policy. I examine the ways in which such power may be acquired and deployed by exploring the use of the word "evidence" and its derivatives in education discourse. Via corpora and discourse analysis of extracts from policymakers' statements, speeches and assertions I examine how "evidence" -- a powerful word in lay use because of its association with research and reason -- is used habitually as a proxy for the specification of actual evidence, simply to add weight to an argument or to impart legitimacy on a policy position. I conclude that the idea of "evidence-based" persists only because of its value in enabling and promoting particular policy agendas.